6976 is a high-reactivity cationic photoinitiator designed for UV-LED or medium-pressure mercury lamp curing of cycloaliphatic epoxides, vinyl ethers and other cationically polymerisable systems. It shows strong absorption at 290 nm (ε ≈ 2×10⁴ L mol⁻¹ cm⁻¹) and efficient photolysis into Brønsted acids that initiate ring-opening epoxidation or vinyl-ether addition with low shrinkage (< 2 %) and excellent through-cure (> 4 mm). The commercial product is normally supplied as a 50 % concentrate in propylene carbonate (density 1.40–1.42 g cm⁻³, water < 1 %) to improve compatibility and reduce viscosity.
Key Physicochemical Data:
Active absorption: 290 nm (methanol)
Density (20 °C): 1.40–1.42 g cm⁻³
Vapour pressure: < 0.003 Pa at 25 °C
Flash point: > 200 °C (closed cup)
Log P (octanol/water): 3.8 (predicted for cation)
Thermal decomposition onset: > 230 °C
Typical Uses:
Cationic UV-curing of ultra-thin (< 1 mil) optical-fiber coatings, clear top-coats and structural adhesives on metal or plastic substrates.
Deep-section or pigmented (black/red) inks and encapsulants where free-radical systems show oxygen inhibition.
Photo-patternable dielectrics and micro-fluidic chips requiring low cure shrinkage and high chemical resistance.
Processing & Dosage:
Recommended addition level: 2–15 % w/w on total formulation; exact level determined by thickness, pigment loading and lamp dose.
Compatible with cycloaliphatic epoxides, vinyl ethers, oxetanes and hydroxyl-functionalised diluents.
Post-bake (80–120 °C, 5–10 min) optional to drive dark-cure and boost conversion.
Quality Specification (Commercial Grade):
Active content: ≥ 50 % (HPLC)
Water content: ≤ 1 % (KF)
Gardner colour: ≤ 7
Chloride: ≤ 100 ppm
Heavy metals: ≤ 20 ppm
Hazard Statement:
Causes skin and eye irritation (H315 + H319). Avoid inhalation of mist; use gloves, goggles and local exhaust. Store in tightly closed containers at 2–8 °C away from light and moisture. SDS available on request.
